Pneumatic stapling device



March 10, 1970 I 1 I D. VOLKMYYANN 35 5 PNEUMATIC STAPLING DEVICE I i Filed Oct. 26,1966

Fig.7

D/ETEP VOL/(MANN TTORNE'YS United States Patent Int. Cl. B25c 1/04 US. Cl. 227-130 2 Claims ABSTRACT OF THE DISCLOSURE A pneumatic stapler of the type having a working cylinder communicating with a surrounding air chamber by means of ports in the cylinder wall is provided with an outlet passage for venting air from the cylinder to the atmosphere during the driving stroke of the piston. The size and location of the vent passage are such as to avoid development of couuterpressure in the cylinder during the driving stroke. The ports in the cylinder wall provide open communication between the cylinder and the air chamber. The piston carries a resilient bumper whichcloses the vent passage when the piston reaches the endof its driving stroke, and the bumper is of smaller diameter than the The present invention relates to a pneumatic stapling device and especially to a portable device operable by compressed air and serving to drive fastening means such as staples. and the like into a work piece by means of a driver which is actuated by a piston operated by compressed air, which piston is returned to its initial position by pneumatic operation.

In the devices providing for a pneumatic return of the piston to its initial position as known in the art, the air displaced in the cylinder by the piston during its driving stroke produces a counterpressure which reduces the efficiency of the stapler.

It is an important object of the present invention to provide a compressed-air operated device of the above type the piston of which is not exposed to any counterpressure resulting from the air which is displaced by said piston. Y

It is another object of the present invention to provide a portable stapler the piston of which is pneumatically returned to its original or initial'positio'n. immediately after the termination of the driving stroke, the quantity of air available for this purpose being used for moving the piston into its initial position.

It is a further object of the invention to provide a portable pneumatic stapler the piston of which receives immediately after termination of its driving stroke, an additional impulse in the direction of its return movement to'the initial position.

These and other objects of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings in which an embodiment of the invention is illustrated by way of an example.

In the drawings FIG. 1 is a side elevation partly in longitudinal section, of a portable hand-operated apparatus operated by compressed air for driving in staples, with the piston in its original or initial position; and

FIG. 2 is a front elevation, partly in cross-section.

Referring to the drawings, FIG. 1 illustrates an apparatus which incorporates this invention. The body 1 of this apparatus is shaped to form a handle section and 3,499,593 Patented Mar. 10, 1970 "ice encloses in its front part 2, a sleeve-shaped working cylinder 3 in which a piston 4 is reciprocably guided. Secured to the lower face of piston 4 is an axially projecting cylindrical bumper 5 manufactured of resilient material, the stepped wall of which has a smaller diameter than the piston 4. The bottom of said piston extends radially beyond the bumper 5 in an annular area 17. The cylinder 3 is enclosed by an air chamber 6 the larger part of which is located in the part of the body I belonging to the handle section. The air chamber 6 communicates with the inside of cylinder 3 through several narrow ports 7 provided approximately in the middle of the longit-udinal extent of the side Wall of cylinder 3 and through several larger ports 8 provided near the cylinder bottom wall 16. In said bottom 16 is arranged a large axial opening 9 which is penetrated, with considerable clearance, by the driver 14 secured to piston 4 and guided in the drive track 11 in the tool nose portion. Via a slot 10 extending parallel to the driver 14 and laterally through the tool nose portion, the opening 9 is in permanent open communication with the atmosphere, as is shown in FIG. 2. The cylinder bottom 16 is mounted in a recess of the front part 2 of the apparatus body and, by an elastic ring 15, is sealed against the housing portion enclosing said bottom. The upper part of cylinder 3 is also sealed, by an elastic ring 15, against the housing portion enclosing it. An air admission conduit 18 is joined to the upper end of cylinder 3. By the usual trigger-actuated control valve 13 the admission, to the cylinder, of air under pressure available from a compressed air system and entering through the socket 12, is controlled.

The cylinder 3 is closed by a threaded cap 19 the bottom face of which is provided with a magnet 20 holding the piston 4 in its initial position.

The drive track 11, the upper or inlet end of which is spaced from the cylinder bottom wall 16 by the intervening slot 10, communicates with a feeding magazine 21 containing the staples joined to form a strip.

In order to drive the staples into a work piece, compressed air is admitted to the air conduit 18 by operation of the control valve 13. As soon as the compressed air has overcome the force of magnet 20, piston 4 is moved in its working direction and driver 14 separates a staple from the lower or outlet end of the staple strip in the magazine 21 and ejects it through the drive track 11 and drives it into the work piece. The air in cylinder 3 which is displaced by the piston 4 during the working stroke is allowed to escape into the atmosphere through the opening 9 and the slot 10. The cross-sectional areas of opening 9 and slot 10 are of such size that all the air which is under the piston 4 in the course of its drive stroke is exhausted into the atmosphere without any hindrance at all. It follows that no counterpressure is allowed to develop in front of the piston 4 and that, at the end of its working stroke, the piston has developed its highest speed and, thus, its full impact force. 1

When the piston 4 has proceeded the larger part of its working stroke, part of the compressed air acting on the upper face of said piston flows through the narrow ports 7 and enters the air chamber 6. At the end of the working stroke the resilient bumper 5 of piston 4 hits the cylinder bottom 16, thus closing the opening 9. The compressed air existing in the air chamber 6 now flows through the large ports 8 and enters the space formed by the lower face of the annular area 17 of piston 4, the outer face of bumper 5, and the inside face of cylinder 3. The size of the air chamber 6 is such that the quantity of compressed air enclosed by said chamber is sufiicient to make the piston 4 return to its initial position. In fact, the compressed air operating on the annular area 17 will move the piston 4 back in sudden bursts, the cylinder space over said piston being vented through the air conduit 18 and the control valve 13. The impulse transmitted to the annular area 17 of piston 4 by the compressed air issuing from the air chamber 6 is so powerful that it suffices to make the piston return to its initial position.

When hitting the cylinder bottom 16 the piston 4 receives, from the resilient bumper attached to its lower face, an additional impulse in the direction of its return movement towards its initial position as, when hitting the cylinder bottom 16, this bumper is compressed and, by its resilience, accelerates piston 4 in the direction of return. Although, right at the beginning of the return movement of piston 4, the bumper 5 releases the opening 9 in the cylinder bottom 16, this will not aifect its rapid return movement, as sufficient acceleration has already been imparted to it by the resilience of the bumper 5. Although the opening 9, now released, offers a way out of the compressed air flowing from the air chamber *6 through the ports 8 into the cylinder 3, this will not cause any waste of compressed air worth mentioning, as, during the return movement of the piston 4, the control valve 13 cuts off the supply of compressed air to the cylinder 3 as well as to the air chamber 6 and merely establishes a communication between the upper part of the cylinder 3 and the tree air.

As soon as the piston 4 has reached its initial position, it is retained there by the magnet in the cap 19 until the next operation causes fresh compressed air to flow into the cylinder 3.

The invention is of particular importance in connection with compressed air operated hand appliances for driving of staples and other fastening means and has, in addition to the advantages of low weight and small dimensions, also that of low manufacturing costs.

It is apparent that the example shown above has been given solely by way of illustration and not by way of limitation and that it is subject to many variations and modifications. All such variations and modifications are to be included within the scope of the appended claims.

What I claim is:

1. In a pneumatic stapling device including a body portion containing a cylinder having a side wall and a bottom wall at one end thereof, a nose portion extending from said bottom wall, staple supply means for supplying staples to said nose portion, a piston reciprocable in said cylinder, a driver secured to said piston and extending through said bottom wall into said nose portion, means in said body portion defining an air chamber around said cylinder, and means for admitting compressed air at the opposite end of said cylinder for moving said piston in a driving stroke from an initial position adjacent said opposite end of said cylinder to a terminal position adjacent said one end of said cylinder at the end of said driving stroke, said side wall of said cylinder having first port means intermediate the ends of said cylinder for admitting said compressed air to said air chamber from the interior of said cylinder during the latter part of said driving stroke and second port means adjacent said one end of said cylinder for admitting compressed air from said air chamber to the interior of said cylinder for eifecting return of said piston from said terminal position to said initial position; the improvement which comprises:

air outlet passage means comprising an enlarged axial opening in said bottom wall and a slot extending laterally through said nose portion and connecting said opening directly with the atmosphere, said passage means comprising the sole restriction to the discharge of displaced air from said cylinder to the atmosphere during the driving stroke of said piston, and said passage means being of such size that substantially. all of the air displaced by said piston during its driving stroke is exhausted to the atmosphere through said passage means, thereby avoiding development of counterpressure tending to hinder the driving stroke of said piston; means in said nose portion defining an elongated con.-

fined drive track for receiving staples from said staple supply means, said drive track having an inlet end communicating with said slot and spaced by said slot from said bottom wall, and said driver extending through said opening and said slot into said inlet end of said drive track in all positions of said piston, whereby during the driving stroke air is vented from said cylinder through said passage means directly to the atmosphere without passing through said drive track and said driver is at all times guided by said drive track; and resilient bumper carried by and projecting axially from said piston for abutting said bottom wall of said cylinder at the end of said driving stroke, the outermost end of said bumper having a diameter sufiiciently large to close said opening when said bumper abuts said bottom wall and the innermost end of said bumper adjacent said piston having a smaller diameter than said piston thereby providing an annular end shoulder on said piston which is exposed to air pressure from said chamber through said second port means for effecting return movement of said piston. 2. The device of claim 1 further characterized in that said port means provide open and unobstructed fluid communication between the interior of said cylinder and said air chamber during the driving stroke of said piston.

References Cited UNITED STATES PATENTS 2,983,922 5/1961 Juilfs 227- 2,985,139 5/1961 Powers et al 227l30 XR 3,170,487 2/ 1965 Juilfs et a1.

3,387,541 6/1968 Bade 227l30 X 3,403,600 10/1968 Bade 227130 X FOREIGN PATENTS 930,364 7/1963 Great Britain.

' GRANVILLE Y. CUSTER, JR., Primary Examiner 

